framework/av: Fix for frame drop in video playback

- Breaks in video playback seen in video clips having audio content
  with sampling rates less than 16kHz.
- While extrapolating real time with system time, the real time is wrongly
  caped.
- Fix this issue by limiting the extrapolated real time only when EOS
  is reached.

Change-Id: I95b6a8f7f1f1fd561c92955cf52151ae2890c9a7
CRs-Fixed: 400398
audioflinger: Add Null pointer check while enabling effects for LPA

- MediaServer is crashing when disabling effects after mediaplayer
object is released.
- EffectChain pointer is de-referenced without NULL check, hence
leading to a mediaserver crash.
- Adding a NULL pointer check before using EffectChain object.

Change-Id: If5ff469445246028046ba65e5ddf3300180318c2
CRs-Fixed: 583305